If both Opus and Explorer are having this problem, the cause will be outside of them. Possibly a shell extension something has installed, or hardware or driver problems.
Have any crash dumps been created? They can sometimes say which component or operation is crashing, and point to a solution.
If you only see freezes and not actual crashes, you can make Windows take a snapshot of the process, which we can often use to see where it is freezing. Doing that for both Opus and Explorer could be useful, to check if they are both freezing in the same component or operation.
Instructions on how to do that are below.
Please also link your account for us to be able to look at those dumps.
While it's happening, please go to Task Manager, then the Details tab, right-click dopus.exe and select Create Dump File.
Do that 4 or 5 times, and it should create something like:
C:\Users\<username>\AppData\Local\Temp\dopus.DMP
C:\Users\<username>\AppData\Local\Temp\dopus (2).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (3).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (4).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (5).DMP
The files will be large, but compress well.
If sending more than one file, using the 7z format instead of zip will give a much reduced size. You can do this via the Archive Files button in Opus.
Please zip or 7z the files and email them to crashdumps@gpsoft.com.au (it's best not to post full dumps publicly to the forum).
Checking the system event log for error messages to do with disks or the filesystem may also be a good idea.